android - 如何检索存储在数据库中的空值？

Question

我正在使用 Sqlite 数据库并为行存储空值。我正在使用此代码在数据库中存储空值:

            ContentValues values = new ContentValues();
            values.put(KEY_NAME,"");
            values.put(KEY_PH_NO,"");           
            values.put(KEY_FOLDER_NAME, contact.getFolderName());
            values.put(KEY_FolderAddress, contact.getParentFolderAddress());
            values.put(KEY_TIME, contact.getTime());    
            values.put(KEY_DATE, contact.getDate());

我正在使用以下查询来检索具有空值的数据库条目:

String selectQuery = "SELECT  * FROM " + TABLE_CONTACTS + " WHERE "+KEY_FolderAddress+" ='"
                     +FileAddress+"'"+" AND "+KEY_FOLDER_NAME+" ='"+FileName+"'"+" AND "+KEY_DATE+" ='"+"0"+"'"
                     +" AND "+KEY_PH_NO+" ='"+""+"'"+" AND "+KEY_NAME+" ='"+""+"'";

但我在检索空值时遇到此异常:

12-25 11:52:40.531: E/Exception:(1990): android.database.sqlite.SQLiteException: unknown error: , while compiling: SELECT  * FROM rules WHERE folderaddress ='/sdcard/Velosys/a' AND folder_name ='a' AND date ='0' AND phone_number ='' AND name ='' Exception occured in getTimeOfTheFolderFromContact() of DatabaseHandlerRule.java

我搜索了很多但没有找到解决方案。请帮助我找到从 sqlite 数据库中检索空值的正确方法。提前致谢

编辑:

I am storing 2 entries with empty values i.e KEY_NAME and KEY_PH_NO

这是表格格式:

String CREATE_CONTACTS_TABLE = "CREATE TABLE " + TABLE_CONTACTS + "("
            + KEY_ID + " INTEGER PRIMARY KEY, " +KEY_NAME+" TEXT, "+ KEY_PH_NO + " TEXT, "
            +KEY_FOLDER_NAME+" TEXT, "+ KEY_FolderAddress + " TEXT, "+KEY_TIME + " TEXT, "+KEY_DATE+" TEXT "+")";
            db.execSQL(CREATE_CONTACTS_TABLE);

Answer 1

您必须使用一些通用值来存储在数据库中:

ContentValues values = new ContentValues();
            values.put(KEY_NAME,"null");
            values.put(KEY_PH_NO,"null");  

请使用此代码检索空值:是的，您是对的，因为“空”值将作为字符串值存储在数据库中。

int i = resultSet.getInt(resultSet.getColumnIndex(columnName));
        String str = resultSet.getString(resultSet.getColumnIndex(columnName));
        boolean bool = resultSet.isNull(resultSet.getColumnIndex(columnName));
        if( str == null )
        {
            return -1;
        }
        return i;